Term unplanned investment Definition: Investment expenditures that the business sector undertakes apart from those they intend to undertake based on expected economic conditions, interest rates, sales, and profitability. Another term for unplanned investment is change in inventories, which result when aggregate expenditures differ from aggregate output. Unplanned investment can be either positive or negative, meaning business inventories can either rise or fall. Should unplanned investment occur, then actual and planned investment differ, aggregate expenditures are not equal to aggregate output, and the macroeconomy is not in equilibrium.